Gauze electrode for a cathode-ray tube

ABSTRACT

A gauze electrode for a cathode-ray tube, in particular a camera tube, in which the aperture of the supporting ring is substantially rectangular the oppositely located sides of which are curved.

United States Patent Hamersma 1 Jan. 14, 1975 GAUZE ELECTRODE FOR A [56]References Cited CATHODE-RAY TUBE UNlTED STATES PATENTS [75] Inventor:Willem Antonius Maria Hamersma, 3,287,585 l1/l966 Rundcls 4113/8)Emmasingel, Eindhoven, Nfitherlands OTHER PUBLlCATlONb Kuseman,Turget-to-Mesh Spacing Means for ()rthi- [73] Assgnee: Ph'hpsCorporatmn, New con Tubes, RCA Technical Notes, August 1965,

York RCA TN No. 630.

[22] Filed: Oct. 9, 1973 Primary ExaminerJames B. Mullins [211 App!404340 Attorney, Agent, or Firm-Frank R. Trifari; Curl P.

Steinhauser [30] Foreign Application Priority Data 0m. 27, I972Netherlands 7214547 ABSTRACT A gauze electrode for a cathode-ray tube,in particular U-S. Cl. a amgra tube in the aperture of the upporting[51] Int. Cl. H01] 29/46 i i b t tially ectangular the oppositelylocated [58] Field of Search 313/65 R, 65 T, 74, 85 R, Sides f which arecurved.

5 Claims, 4 Drawing Figures GAUZE ELECTRUDIE FOR A CATHODE-RAY TUBE Theinvention relates to a gauze electrode for a cathode ray tube, whichelectrode is arranged at a small distance parallel to a signal plate andwhich is supported at the edge by at least one supporting ring, measuresbeing taken to reduce microphony" interferences which may occur as aresult of vibrations of the gauze electrode. The invention relates inparticular to a gauze electrode for a camera tube of the vidicon type.

It has already been tried in various manners to reduce the microphonyeffect of such a gauze electrode, for example, by providing rods orplates which, if desired, also serve as spacing members between gauzeand signal plate (see British Patent Specification Nos. 984,673; 948,944and 1,094,186) or by reinforcing the gauze by providing ribs in thegauze (German Patent Specification No. 1,237,168), However, these knownmeasures are complicated and attenuate the vibrations of the gauzeelectrode only to an unsatisfactory extent.

A much simpler solution which provides a much stronger attenuation ofthe undesired vibrations of the gauze electrode is obtained if,according to the invention, the inner edge of at least one supportingring of the gauze electrode encloses an aperture which mainly is in theform of a rectangle of which at least two oppositely located sides arecurved, the wires of the gauze extending mainly according to thediagonals of the rectangular aperture. The corners of the rectangle arepreferably rounded off, so as to be able to better use the surface ofthe gauze. The curved sides of the aperture preferably extend convexrelative to the centre of the aperture. Preferably, all four sides areshaped in this bent manner. The radius of the curved sides is preferablyapproximately equal to the radius of the outer edge of the supportingring.

A damping member of thin aluminum foil is known from the U.S. Pat. No.3,287,585 which is provided as a spacing member between gauze and signalplate. It is stated that the aperture of said foil may be irregular andthat finger-shaped projections may be present, if desired. However, suchprojections can only be used if the material thereof consists of a thinfoil since otherwise they damage the gauze.

The invention will be described in greater detail with reference to theaccompanying drawing, of which:

FIG. 1 is a longitudinal sectional view of a vidicon tube,

FIG. 2 shows an embodiment of a supporting ring for a tube withrectangular picture scanning, and

FIG. 3 shows an embodiment of a supporting ring suitable for scanningboth a rectangular and a circular disk-shaped picture, while FIG. 4 is apart of a cross-sectional view of a gauze electrode according to theinvention.

Reference numeral 1 in FIG. 1 denotes the wall of a vidicon camera tubewhich is closed by a glass plate 2. A photosensitive signal electrode 3is present on the inside of the plate 2. The gauze electrode 4 isprovided parallel to the electrode 3 and at a few millimeters dis tancetherefrom. The gauze 4 consists, for example, of wires of nickel orcopper having a thickness of 4 p. and a center distance of 36 t. Insteadof wires, the gauze electrode 4 may also be a perforated plate.

The gauze 4 is clamped between two supporting rings 5 and 7 which aresecured together by means of a numher of spot welds along thecircumference or by solder ing or diffusion. The material of the ring 5has a thickness of, for example, 0.5 mm, the material of the ring 7 is,for example, 0.1 mm thick. The rings 5 and 7 consist of molybdenum whennickel gauze is used and of a chromium-nickel alloy when copper gauze isused. Furthermore, an electron lens 6 is provided in the tube.

The supporting ring 7 shown in FIG. 2 comprises a mainly rectangularaperture the sides 8 and 9 of which are convex relative to the center ofthe aperture. The corners are rounded so as to obtain a better use ofthe gauze surface. The sides 9 are longer than the sides 8 so that thiselectrode is mainly suitable for scanning an elongate rectangularpicture surface.

In the embodiment shown in FIG. 3, all sides 8 of the aperture are thesame so that this electrode is suitable both for scanning circulardisk-shaped pictures and for scanning rectangular pictures. The wires ofthe gauze 4 extend approximately according to the diagonals of themainly rectangular aperture. In the case in which the gauze electrodeconsists of a perforated plate, the holes are provided in rows whichextend approximately in the direction of the diagonals of the mainlyrectangular aperture of the ring.

As is shown in FIG. 4, the parts of the sides 8 and 9 projectinginwardly may be bent out of the plane of the ring so that they slightlypress on the gauze 4 and thus intensify the damping effect. It has beenfound that the damping of a ring formed according to the invention isapproximately 20 times more effective than in the case in which a ring 7is used having a rectangular hole with straight sides.

Although two particular embodiments of the invention have beendescribed, other shapes for the aperture of the ring 7 may be usedwithout departing from the scope of this invention. For example, arectangle may be used having two straight and two oppositely locatedcurved sides, or the corners may not be rounded off, in which case acushion-shaped aperture is formedv The use of an aperture having morethan 4 sides is more unfavourable according as the number of sidesincreases, since the circumference of the aperture increasinglyapproaches the circle, which is unfavourable with respect to theoccurrence of vibrations.

Besides for camera tubes, the invention is also of importance for othercathode-ray tubes, for example, oscillograph tubes, and the like.

What is claimed is:

l. In a cathode-ray tube having a target electrode at one end of anenvelope and a gauze electrode spaced from said target electrode, theimprovement comprising at least one annular member spaced from saidtarget for supporting said gauze electrode with reduced microphonicinterference, said annular member having an inner edge enclosing asubstantially rectangular aperture having at least two oppositelylocated curved sides, said gauze electrode comprising wires extendingsubstantially parallel to the diagonals of said rectangular apertures.

2. A gauze electrode as claimed in claim 1, wherein the rectangularaperture has rounded corners.

3. A gauze electrode as claimed in claim 1, wherein the curved sides areconvex towards the center of the aperture.

4. A gauze electrode as claimed in claim 3, wherein the convex shapedparts of the supporting ring are bent out of the plane of the ring inthe direction of the gauze.

5. A gauze electrode as claimed in claim 4, wherein the radius of thecurved sides is approximately equal to the radius of the outer edge ofthe supporting ring.

1. In a cathode-ray tube having a target electrode at one end of anenvelope and a gauze electrode spaced from said target electrode, theimprovement comprising at least one annular member spaced from saidtarget for supporting said gauze electrode with reduced microphonicinterference, said annular member having an inner edge enclosing asubstantially rectangular aperture having at least two oppositelylocated curved sides, said gauze electrode comprising wires extendingsubstantially parallel to the diagonals of said rectangular apertures.2. A gauze electrode as claimed in claim 1, wherein the rectangularaperture has rounded corners.
 3. A gauze electrode as claimed in claim1, wherein the curved sides are convex towards the center of theaperture.
 4. A gauze electrode as claimed in claim 3, wherein the convexshaped parts of the supporting ring are bent out of the plane of thering in the direction of the gauze.
 5. A gauze electrode as claimed inclaim 4, wherein the radius of the curved sides is approximately equalto the radius of the outer edge of the supporting ring.